Although it was known that RMSF was caused when the Rickettsia rickettsii bacteria infected a Dermacentor andersoni tick that then bit a human, more questions remained. Was the bacteria spread by other species of ticks? And exactly how did the ticks get infected? To find out where the ticks were picking up the infection and to answer a number of other questions, ticks had to be collected in the wild.
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A staff member of the Canyon Creek Schoolhouse Laboratory—possibly Dr. Ralph Parker, C.M. Salisbury, or George Cowan—dragged a white flannel flag over brush and grass to gather ticks in the Bitterroot Valley, Montana. He wore a white jump suit over his regular clothes, tucking his pant legs into the top of his high, laced boots. When they returned from such outings, the men would check each other closely in case a tick had attached itself to one of them.
Image: Office of NIH History and Stetten Museum, 1522
In 1923, a mountain goat (not perhaps this mountain goat kid) taken by George Cowan had over 1,000 ticks engorged ticks on it. It was with these ticks that Dr. Roscoe Spencer came up with his idea for an RMSF vaccine.
Image: Montana Memory, 264
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Constant collecting
As RMSF gave up its mysteries, researchers still had other tick-borne diseases to study. They constantly collected ticks where outbreaks of Rickettsial diseases occurred.
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In 1929, LeRoy Jones, Harley G. Sargent, Harry L. Sargent, and James Kerlee posed at the top of Blodgett Canyon in the Bitterroot Range. Each holds several white cloth bundles tied to a stick for specimen collection. James Kerlee’s brother, Arthur LeRoy Kerlee, had died the year before of RMSF that he had acquired in the laboratory.
Image: Office of NIH History and Stetten Museum, 1449
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Inventing the Vaccine
Dr. Roscoe Spencer came to the Canyon Creek Schoolhouse laboratory from Washington, D.C., in spring 1921, when the ticks were out. After the laboratory’s field workers collected ticks, Spencer would test the ticks for RMSF by taping them to a guinea pig; if the guinea pig came down with RMSF, the ticks were infected. But this process was messy and dangerous and slow, so he decided to grind up the ticks and inject them under the skin of the guinea pigs. Still, none of them got sick. Then he took samples from guinea pigs that were sick with RMSF. He injected the samples into guinea pigs that had been injected with ground-up ticks and into those guinea pigs that had not. The guinea pigs that had previously been injected with the ground-up ticks did not get sick.
